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Message-ID: <87haralb0u.fsf@xmission.com>
Date: Thu, 06 Sep 2012 21:20:01 -0700
From: ebiederm@...ssion.com (Eric W. Biederman)
To: David Miller <davem@...emloft.net>
Cc: <netdev@...r.kernel.org>, "Serge E. Hallyn" <serge@...lyn.com>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next] scm: Don't use struct ucred in NETLINK_CB and struct scm_cookie.
Passing uids and gids on NETLINK_CB from a process in one user
namespace to a process in another user namespace can result in the
wrong uid or gid being presented to userspace. Avoid that problem by
passing kuids and kgids instead.
- define struct scm_creds for use in scm_cookie and netlink_skb_parms
that holds uid and gid information in kuid_t and kgid_t.
- Modify scm_set_cred to fill out scm_creds by heand instead of using
cred_to_ucred to fill out struct ucred. This conversion ensures
userspace does not get incorrect uid or gid values to look at.
- Modify scm_recv to convert from struct scm_creds to struct ucred
before copying credential values to userspace.
- Modify __scm_send to populate struct scm_creds on in the scm_cookie,
instead of just copying struct ucred from userspace.
- Modify netlink_sendmsg to copy scm_creds instead of struct ucred
into the NETLINK_CB.
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
include/linux/netlink.h | 3 ++-
include/net/scm.h | 23 +++++++++++++++++++----
net/core/scm.c | 17 +++++++++++------
net/netlink/af_netlink.c | 2 +-
4 files changed, 33 insertions(+), 12 deletions(-)
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index c9fdde2..df73cf4 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -153,6 +153,7 @@ struct nlattr {
#include <linux/capability.h>
#include <linux/skbuff.h>
+#include <net/scm.h>
struct net;
@@ -162,7 +163,7 @@ static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb)
}
struct netlink_skb_parms {
- struct ucred creds; /* Skb credentials */
+ struct scm_creds creds; /* Skb credentials */
__u32 pid;
__u32 dst_group;
struct sock *ssk;
diff --git a/include/net/scm.h b/include/net/scm.h
index 079d788..000b6f7 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -12,6 +12,12 @@
*/
#define SCM_MAX_FD 253
+struct scm_creds {
+ u32 pid;
+ kuid_t uid;
+ kgid_t gid;
+};
+
struct scm_fp_list {
short count;
short max;
@@ -22,7 +28,7 @@ struct scm_cookie {
struct pid *pid; /* Skb credentials */
const struct cred *cred;
struct scm_fp_list *fp; /* Passed files */
- struct ucred creds; /* Skb credentials */
+ struct scm_creds creds; /* Skb credentials */
#ifdef CONFIG_SECURITY_NETWORK
u32 secid; /* Passed security ID */
#endif
@@ -49,7 +55,9 @@ static __inline__ void scm_set_cred(struct scm_cookie *scm,
{
scm->pid = get_pid(pid);
scm->cred = cred ? get_cred(cred) : NULL;
- cred_to_ucred(pid, cred, &scm->creds);
+ scm->creds.pid = pid_vnr(pid);
+ scm->creds.uid = cred ? cred->euid : INVALID_UID;
+ scm->creds.gid = cred ? cred->egid : INVALID_GID;
}
static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
@@ -110,8 +118,15 @@ static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg,
return;
}
- if (test_bit(SOCK_PASSCRED, &sock->flags))
- put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(scm->creds), &scm->creds);
+ if (test_bit(SOCK_PASSCRED, &sock->flags)) {
+ struct user_namespace *current_ns = current_user_ns();
+ struct ucred ucreds = {
+ .pid = scm->creds.pid,
+ .uid = from_kuid_munged(current_ns, scm->creds.uid),
+ .gid = from_kgid_munged(current_ns, scm->creds.gid),
+ };
+ put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(ucreds), &ucreds);
+ }
scm_destroy_cred(scm);
diff --git a/net/core/scm.c b/net/core/scm.c
index 5472ae7..64b41d8 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -155,19 +155,21 @@ int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
break;
case SCM_CREDENTIALS:
{
+ struct ucred creds;
kuid_t uid;
kgid_t gid;
if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
goto error;
- memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
- err = scm_check_creds(&p->creds);
+ memcpy(&creds, CMSG_DATA(cmsg), sizeof(struct ucred));
+ err = scm_check_creds(&creds);
if (err)
goto error;
- if (!p->pid || pid_vnr(p->pid) != p->creds.pid) {
+ p->creds.pid = creds.pid;
+ if (!p->pid || pid_vnr(p->pid) != creds.pid) {
struct pid *pid;
err = -ESRCH;
- pid = find_get_pid(p->creds.pid);
+ pid = find_get_pid(creds.pid);
if (!pid)
goto error;
put_pid(p->pid);
@@ -175,11 +177,14 @@ int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
}
err = -EINVAL;
- uid = make_kuid(current_user_ns(), p->creds.uid);
- gid = make_kgid(current_user_ns(), p->creds.gid);
+ uid = make_kuid(current_user_ns(), creds.uid);
+ gid = make_kgid(current_user_ns(), creds.gid);
if (!uid_valid(uid) || !gid_valid(gid))
goto error;
+ p->creds.uid = uid;
+ p->creds.gid = gid;
+
if (!p->cred ||
!uid_eq(p->cred->euid, uid) ||
!gid_eq(p->cred->egid, gid)) {
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 7cb7867..6473267 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1398,7 +1398,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
NETLINK_CB(skb).pid = nlk->pid;
NETLINK_CB(skb).dst_group = dst_group;
- memcpy(NETLINK_CREDS(skb), &siocb->scm->creds, sizeof(struct ucred));
+ NETLINK_CB(skb).creds = siocb->scm->creds;
err = -EFAULT;
if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {
--
1.7.5.4
--
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